Question about 1989 GMC Sierra

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89 GMC sierra only starts when tps and map sensor unplugged

I have replaced tps and checked all fire and fuel. replaced map sensor with another(not new but from working vehicle) and no change. Checked temp sensor, control module, and coil as well.

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  • ajax5
    ajax5 Feb 18, 2013

    update: also I have watched the injectors, they seem to loose pressure when I plug in the map or tps.



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  • 2 Answers


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Posted on Jan 02, 2017

  • 11896 Answers

SOURCE: my son's gmc 4.3l hesitates upon acceleration. I

do you have any check engine lights on? If you do, that is the first thing I would have checked. It does sound like plugged EGR, vacuum leak, or bad TPS

Posted on May 15, 2009

  • 1 Answer

SOURCE: 97 gmc sierra no fuel no spark replaced ign module

1996 GMC 1500 Pickup.
Replaced Coil, Dist cap/Rotor, Ign Mod & pick-up.
All showed to be bad with OHM meter.

20A ECM-B fuse keeps blowing out and I'm afraid to burn these new parts up....


Posted on May 19, 2009

  • 358 Answers

SOURCE: I have 96 gmc 350 vortec. missing really bad. Ive

ou need to check compression on all the cly. do you know which cly is dead?

Posted on Jun 12, 2009

  • 1168 Answers

SOURCE: I have A 1991 GMC SIERRA, 350,no fuel no spark,

Do you have power to the injectors? One of the wires to the injector will come on for a couple seconds as soon as you turn the key to the on position.The computer controls the ground side. If you do not get power to one of them start looking for an open circuit. The same power source will also go to your ignition coil and ignition module. If you do not have power on the pink wire to the coil apply a temporary fused battery power source to it and give it a try, this will also power up the injectors.
Check it out and let me know.

Posted on Oct 29, 2009

  • 3854 Answers

SOURCE: 1991 4.3L GMC Jimmy S-15 will not start. Turns

You need 3 things.
Good hot blue spark to all plugs.
Good gasoline and proper fuel pressure. 13-13.5 lbs on your TBI
If you have all 3 then move on to injector pulse to both injectors.

Keep me posted and recheck your spark plug wire to make sure they are not crossed. firing order 1-2-3-4-5-6 cylinder # passenger side 1-3-5 front to back. cylinder # drivers side 2-4-6 front to back
distributor #1 is located at the 7 o"clock and rotates clock wise so next distributor post on the right working clock wise is #2. Good luck and hope this helps.

Posted on Jan 05, 2010

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My 1991 gmc sierra will start but i have to feather the gas if I can get it to idle, the MAP sensor needs to be unplugged. I have changed the MAP 3 times with spares I had around.

Changing parts is not a solution or fix

Testing a vehicle to find a problem is

Once a problem is found, then the solution is
usually there in front of you

It starts
Is the fuel pressure correct?
Feathering the gas,that would pertain to the TPS Sensor
Was that tested?
MAP-no control over that,do you have vacuum leaks
& were any of the maps tested & correct for your elevation
or vehicle specs

Spark Plugs Good
Rotor & Cap Clean
Vacuum Leaks?

Got an IAC Valve at base of throttle body to clean or replace?

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I have a 90 GMC Sierra, 5.7 ltr, 2 wheel drive, 1/2 ton. I recently replaced the ESC module ,MAP sensor, and TPS, because they coded out... I also replaced the distibutor as well. I was running well this...

Try spraying a couple shots of carb spray down the throttle body while a helper cranks it over. If it starts and runs for a couple of seconds check fuel pressure and the resistance of the injectors.

I’m happy to assist further over the phone at

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1995 GMC Sierra

Just a thought, have you checked yout TPS(throttle position sensor)? I had similar problems with my 89 GMC Jimmy 4.3l, however a code 44 is strange. Also check to see if your problems go away if you advance the timing a few degree's.

Hope this helps

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